1. Field of the Invention
The present invention relates to a sheet processing apparatus that performs postprocessing on a sheet discharged from an image forming apparatus such as a copy machine, printer or multi-function peripheral (MFP).
2. Description of the Related Art
Recently, some of image forming apparatuses have a sheet postprocessing apparatus provided next to the image forming apparatus body in order to perform postprocessing such as sorting sheets after image formation and staple processing on sheets. There are also apparatuses that discharge a sheet bundle folded in two.
JP-A-2004-284750 discloses sheet postprocessing to bind sheets in a double-leaved form. In this example, a pair of folding rollers and a folding plate are provided, and sheets are pushed out to the pair of folding rollers by the folding plate, thus folding the sheets at their center. Also, before folding at the center, perforation forming means having multiple needles are pressed to the sheets and perforations are formed on the sheets.
Moreover, JP-A-2004-231422 discloses a sheet preparation system that drills or forms perforations on sheets. As the perforation forming means in this example, a rotary drilling wheel having a backer roll is applied, for example. However, its specific configuration is not described.
The two examples described above also have a problem that it is difficult to fold sheets when the sheets have a large thickness or the number of sheets is large in the case of forming perforations.
The present invention provides a sheet processing apparatus that has a finisher having a sheet folding mechanism and that is capable of forming a folding line such as perforations in advance in accordance with the need when folding sheets.